zchunk, zsync, and casync spring to mind. zchunk and zsync require support for range queries but casync splits the chunks into multiple files. https://github.com/zchunk/zchunk http://zsync.moria.org.uk/ https://github.com/systemd/casync

The linux RPM world has "delta RPMs" which lets you ship much smaller packages when updating. I don't see any blocker to delivering these through a CDN. Not sure if this is quite what you were asking.

The closest you'd come to such a setup is a squid proxy with some prefetching (besides bittorrent, which CDNs don't support until IPFS is a first class citizen).